On-board aircraft weight transducer with mechanical offset adjustment

ABSTRACT

An externally-mounted strain-gage transducer for sensing aircraft weight components in response to load-induced deformations of a support such as an axle, truck beam, or the like, is of an elongated form with end lugs designed for bolting to cooperating horizontally-spaced lugs integral with the support, the transducer end lugs each being provided with an adjustably-deformable hole-and-slot type symmetrical flexural connection by which the transducer ends may be raised or lowered wholly in the desired vertical direction to offset effects such as those of otherwise-unavoidable installation zero shift.

United States Patent Laimins 111 3,797,302 51 Mar. 19, 1974 ON-BOARDAIRCRAFT WEIGHT TRANSDUCER WITH MECHANICAL OFFSET ADJUSTMENT Inventor:

Assignee:

Filed:

Appl. No.:

Eric Laimins, Belmont, Mass.

BLH Electronics, Inc., Waltham,

Mass.

June 21, 1972 US. Cl. 73/885 G01l 1/22 Field of Search 73/885 R, l B,65, 100;

Attorney, Agent, or Firm-James E. Mrose 5 7] ABSTRACT Anexternally-mounted strain-gage transducer for sensing aircraft weightcomponents in response to load-induced deformations of a support such asan axle, truck beam, or the like, is of an elongated form with end lugsdesigned for bolting to cooperating horizontally-spaced lugs integralwith the support, the transducer end lugs each being provided with anadjustably-deformable hole-and-slot type symmetrical flexural connectionby which the transducer ends may be raised or lowered wholly in thedesired vertical direction to offset effects such as those of otherwise-[56] References Cited UNITED STATES PATENTS unavoidable installationzero shift.

3.464.259 9/1969 Farr 73/885 R 8 Claims, 4 Drawing Figures 7 I 7b 8b I 69 75 l b 6. M

ON-BOARD AIRCRAFT WEIGHT TRANSDUCER WITH MECHANICAL OFFSET ADJUSTMENTBACKGROUND OF THE INVENTION The present invention relates toimprovements in the precision measurement of vehicle loadings, such asthose which are characterized in the external deformations of axles ortruck beams of aircraft and the like, and, in one particular aspect, tonovel and improved external on-board aircraft weighing transducers whichare lug-mounted to the exteriors of landing-gear structure by way ofsubstantially rigid and yet adjustablydeformable connections permittingcompensatory mechanical displacements of the transducer to be introducedand maintained accurately.

The art of weighing and calculating center-of-gravity of aircraft inresponse to measurements of weightinduced elastic distortions of theirsupports has been well developed, and has included evolutions ofstraingaged sensing devices designed for both external and internalmounting in relation to support structures such as axles. With knowledgeof the weights effective at each of the points of support by the variouslanding gear, both total craft weight and locus of its c.g. can readilybe calculated, by way of associated computing networks, as importantaids to safe and efficient aircraft operation. Similarly, loadings ofother type of vehicles can be determined using comparable on-boar orpermanently-installed sensors.

An underlying principle associated with many of such sensors ortransducers is that an auxiliary elasticallydeformable gaged element,such as a miniature beam, can be made to witness minute deformationsrelated to those of one section of an axle, for example, if it is verysecurely fastened with that support at a pair of horizontally-spacedpositions, and that these elasticallyobserved deformations can in turncause appropriatelylocated electrical strain gages to develop bridgesignals which will precisely characterize the weight being sustained viathat axle. Various means have been provided for making the needed securefastenings, which are essential to repeatability of performance andwhich must be capable of withstanding severe shock and vibration as wellas other harsh environmental conditions of use. Inevitably, however, theinstallation of such transducers by way of such fastenings entails somemisalignments or distortions or lack of mechanical precision, with theresult that the prefabricated transducers exhibit strains erroneouslysimulating conditions to be measured, or socalled installation zeroshift. In some situations the problems are compounded by the need tooffset the effects of tare, i.e., to have the transducer itself makeallowance for the unloaded weight of the vehicle.

Transducers of the type under discussion are intended to respond tovertical components of loading forces, such that spurious forcesunrelated to weight will not cause measurement error. Likewise, it iscomparably important that the transducers not be twisted or bent indirections which could lead to such error when the transducer is somehowmechanically compensated to offset the aforementioned installation zeroshift or tare. Other known techniques for attempting such mechanicalcompensation have included interleaved washers which could be squeezedinto a tightened and locked coupling between the end of a transducer andits support( US. Pat. No. 3,426,586), and an adjustable set screw fordeflecting the end of a cantilevered beam (U.S. Pat. No. 3,327,270), andan adjustable wedge-shaped pre-load bolt for shifting positions of apre-load finger at the end of a cantilevered bar (U.S. Pat. No.3,494,181), and adjustable colleting for an inside-axle transducer (U.S.Pat. No. 3,625,053). Those transducer-support arrangements which involveseparate relatively-movable parts are prone to difficulty in that severeshock, vibration and extremes of temperature can readily cause them tofall out of. proper adjustment, and, accordingly, the present teachingsare concerned with improved supports involving wholly integralconnection members, the related needs for fine positional trimming beingaccommodated by way of adjustable symmetrical flexures whichadvantageously avoid movements of the transducer in unwanted directions.

SUMMARY It is one of the objects of the present invention to providenovel and improved support of on-board weight transducers, involving ahigh degree of structural integrity while at the same time enablingprecise adjustments for compensation of installation zero shift and/ ortare.

A further object is to provide relatively simple and low-costtransducer-mounting connections in which flexures associated withexpandible or compressible slotting integrally couple the ends of atransducer with its support and are minutely deformable to move thetransducer ends only in substantially one plane for purposes ofintroducing compensating mechanical offsets.

By way of a summary account of practice of this invention in one of itsaspects, an aircraft landing-gear truck beam or the like, equipped witha pair of horizontally-spaced external integral mounting lugs, is unitedwith a generally-elongated transducer having electrical-resistancestrain gages bonded to selected surfaces, each end of the transducerbeing joined with a substantially rigid connector shaped for boltingwith one of the mounting lugs, and each such connector having ahorizontal slot dividing a portion between the positions of the lug andtransducer-end junctions into two vertically-spaced symmetricalflexures; spreading or compressing the slot, by way of an adjustablebolt, causes the associated transducer end to be moved slightly only insubstantially the vertical direction, with consequent adjustment of thestressed state of the installed transducer.

BRIEF DESCRIPTION OF THE DRAWINGS Although the aspects and features ofthis invention which are considered to be novel are expressed in theappended claims, further details as to preferred practices and as to thefurther objects and features thereof may perhaps be most readilycomprehended through reference to the following description taken inconnection with the accompanying drawings, wherein:

FIG.- 1 is a topplan view of part of an aircraft truck beam, partly incross-section, having external lugs mounting a strain-gage transducer byway of connectors affording offset in accordance with the presentinvention;

FIG. 2 provides a side view of the assembly shown in FIG. 1;

FIG. 3 is a partly cross-sectional transverse view of the same assembly,taken along section line 33 in FIG. 2; and

FIG. 4 is a partly cross-sectioned transverse view, comparable to thatof FIG. 3, ofa like assembly including a modified version of anadjustable connector between the truck beam and transducer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the assembly appearing inFIGS. 1-3, weight responses of a vehicle-supporting structure 5, shownspecifically as part of an aircraft landing-gear truck beam, exhibitthemselves as minute deflections of that beam, whereby, atlongitudinally-spaced horizontal positions of the integral external lugs6 and 7, there will be relative displacements, in the verticaldirections, which can be sensed by an externally-mounted horizontalelongated strain-gaged transducer 8 fixed securely with those two lugs.A truck beam of the type under consideration, or a corresponding axle ofan aircraft or other vehicle, is normally disposed in a substantiallyhorizontal orientation, between the body of the vehicle and theunderlying ground surface on which its rests, and an optimum locationfor the associated elongated horizontal transducer is in the horizontalplane including the neutral axis of the beam or axle. That neutral axislies in the plane defined by the lines N.A.-N.A. in FIGS. 2 and 3, and,in accordance with one preferred practice, another correspondingtransducer, supported on like lugs, is mounted (not shown) at thediametricallyopposite position along the same beam or axle. In oneaircraft construction, beam may have an outer diameter of about 9inches, is hollow, and has a wall thickness of about /2 inch.

Although it is theoretically possible to determine weight responses byway of strain gages applied directly to an axle, rather than to employauxiliary transducers, the latter approach is preferable for well-knownreasons in many cases, among these being the facts that critical gageplacements and bonding and the wiring and fastening of associatedcabling can best be achieved under closely-controlled manufacturingconditions, and that known transducers of various configurations canbetter develop the kinds and locations of strains which lend themselvesto optimum gaging and translations of strains into desired measurements.Transducer 8, although not intended to be limited to a particularconfiguration, may, for example, have a relatively deformable sensingmid-section element 8a which is of simple rectangular steel beam form,or may be of another configuration such as that of theparallelogram-beam described in my US. Pat. No. 2,866,059; theassociated gaging (not shown) of such an element is in accordance withknown practices, as is also the electrical bridge circuitry or the likeassociated with measurement indications via such gages. Transducermid-section 8a is integral with more rigid force-transmitting endportions, 8a and 8c, by which the deformations within elastic limits ofthe nearby portion of beam 5 are to be translated into relateddeformations of that section, and, for the latter purposes, those endportions must of course be held in rigorously fixed relation to the twobeam lugs 6 and 7.

The transducer unit is capable of installation and removal from thelugs, because of the fasteninigs thereto by way of bolts 6a and 7a, but,rather than being fastened directly to the end portions 8b and 8c, thesebolts are instead secured to yet further transducer end parts, 9 and 10,which are of a predetermined split configuration affording limitedadjustability in the mounting. End parts 9 and 10 serve as substantiallyrigid connectors for transducer rigid end portions 8b and 8c,respectively, and the latter may be welded integrally with them orotherwise immovably fixed with them; the locus of one of these, 8b, inrelation to connector 9, is shown by dashed line-work 8bb in FIG. 3.From the latter FIGURE. it is evident that the transducer end part 8b isunited with the main body 9a of the connector, but that this main bodyis in dependent relation to a bifurcated portion 917 consisting ofbranches 9c and 9d separated by a slot 9e and further having the innerend of the slot stress-relieved by a larger transverselydrilled hole 9f.The lower one of these branches, 9d, abuts the top of truck-beam lug 7,and is held securely with it as the result of its threaded connectionwith lug 7a. The companion upper branch, 90, is capable of beingcompressed downwardly by a nut 71; on the same bolt, 7a, which passesfreely through an accommodating hole in branch 90. As the nut 7b istightened, the two branches 9c and 9d of the bifurcated portion aredrawn closer together, that action being accommodated by the twoflexures 9g and 9h developed between hole 9f and the upper and lowersurfaces of that bifur-' cated portion. Because lower branch is heldfixed in relation to the lug 7, the resulting displacement must bedownward and main body protion 9a is thus shifted downwardly, ascharacterized by dashed linework 9aa, carrying transducer end part 8bwith it. Connector 10 is constructed similarly, and functionscomparably, whereby transducer end part 8c may be displace downwardly bycontrolled amounts by way of its associated adjusting nut 6b.

When the transducer is being installed, the bolts 6a and 7a aretightened to secure the end connectors 10 and 9 with beam lugs 6 and 7,and, because of such factors as the likelihood that these lugs may nothave perfect alignment with the transducer connectors, the gages of thedistorted transducer will tend to cause erroneousoutput to appear wherenone should be present. Cabling 11 connects the transducer gages toremote electrical indicating circuitry to develop these outputs. One orboth of nuts 7b and 6b is then tightened, and the resulting downwarddisplacements of the transducer ends will cause the distortion to beoffset and the erroneous installation zero shift to be compensated.Importantly, this adjustment procedure entails displacements of thetransducer ends only in one direction, namely the vertical in the caseunder discussion, such that the transducer is not twisted or bent inother error-inducing directions. Force arrows F1 and F2 in FIG. 2characterize load-induced forces which the deflected truck beam mayexert upon the installed transducer. In those cases where it is desiredto offset the unloaded vehicle weight or tare forces, the same kind ofnut adjustments as have just been described also provide a means for sodoing.

The modification exemplified in FIG. 4 illustrates a generally similararrangement in which, for convenience, certain of the same orfunctionally corresponding portions are designated by the same referencecharacters employed in the preceding FIGURES, with distinguishingsingle-prime accents added. There, the main body 9a of one of thetransducer end connectors 9' itself forms one of the branches (lower) ofa bifurcated portion 9b, and the top brance 9c is separated from it bythe slot 9e and the associated drilled hole 9f The relatively rigidjunction of these two branches, 9i, is secured to truck-beam lug 7' bythe bolt 7a. When a set screw 12, threadedly engaged with branch 90, istightened to spread the two branches, the main body part 9a necessarilymoves downwardly somewhat, to a position characterized by dashedlinework 9aa, while the upper branch moves upwardly, and, as before, amechanical offset is achieved for compensation for installation zeroshift and/or tare.

Preferably, the two branches of the bifurcated portion of eachadjustable connector are joined together and with the remaining part ofthe connector by way of flexures, such as 9g and 9h in FIG. 3, which aresubstantially the same, or symmetrical, mechanically. However, similareffects can be realized without perfect symmetry.

It should be understood that the specific practices and preferredembodiments herein referred to have been offered by way of disclosurerather than limitation, and that various modifications, additions andsubstitutions may be effected by those skilled in the art withoutdeparture from these teachings; it is therefore aimed in the appendedclaims to embrace all such variations as fall within the true spirit andscope of this invention.

What I claim as new and desire to secure by letters Patent of the UnitedStates is:

1. On-board vehicle weight transducer apparatus responsive to elasticdeformation of a support such as a truck beam or axle for the vehicle,comprising an elongated transducer including a relatively deformablestrain-gaged element and relatively rigid connectors at the ends of saidelement, means for securing said connectors with such a support atdifferent longitudinallyspaced positions therealong, at least one ofsadi connectors including an integral bifurcated portion the branches ofwhich are separated from one another and means for adjusting the spacingbetween said branches, the junction of said bifurcated portion and oneof the branches of said portion being fixed in relation to differentones of the support and an end of said element, whereby adjustment ofsaid spacing between said branches results in displacement of said endand the support in substantially one direction.

2. On-board vehicle weight transducer apparatus as set forth in claim 1wherein said bifurcated portion is formed by a slot and an enlarged holeat the closed end of the slot, material between the hole and nearbyexternal surfaces of said connector being of reduced crosssection andthereby forming two relatively deformable flexures one on each side ofthe slot.

3. On-board vehicle weight transducer apparatus as set forth in claim 1wherein siad junction is fixed in relation to an end of said element,and wherein said securing means mounts one of said branches in fixedrelation to the support at one of the longitudinally-spaced positionstherealong.

4. On-board vehicle weight transducer apparatus as set forth in claim 3wherein said junction is integrally united with said end of saidelement, wherein said means for adjusting the spacing between sa dbranches comprises a nut and bolt for adjustably drawing said branchescloser together, and wherein said bolt further mounts said one of saidbranches in said fixed relation to the support.

5. On-board vehicle weight transducer apparatus as set forth in claim 1wherein said one of said branches is fixed in relation to an end of saidelement, and wherein said securing means mounts said junction in fixedrelation to the support at one of said positions.

6. On-board vehicle weight transducer apparatus as set forth in claim 5wherein said one of said branches in integrally united with said end ofsaid element, and wherein said means for adjusting said spacing betweensaid branches comprises a set screw threadedly engaged with one of saidbranches and having an end abutting the other of said branches, wherebyadjustment of said set screw adjustably spreads said branches apart.

7. On-board vehicle weight transducer apparatus as set forth in claim 1for use with such a support which includes a pair of lugs externallythereof and integrally therewith, one at each of the spaced positionsand in substantially horizontal alignment, and wherein said securingmeans secures said connectors to the external lugs of the support, theone of said junction and branches which is fixed in relation to thesaidend of said element being integrally united therewith.

8. On-board vehicle weight transducer apparatus as set forth in claim 7for use with such a support in which the lugs are substantially alignedwith a horizontal plane including the neutral axis of the support, andwherein both of said connectors include an integral bifurcated portionand are substantially the same.

1. On-board vehicle weight transducer apparatus responsive to elasticdeformation of a support such as a truck beam or axle for the vehicle,comprising an elongated transducer including a relatively deformablestrain-gaged element and relatively rigid connectors at the ends of saidelement, means for securing said connectors with such a support atdifferent longitudinally-spaced positions therealong, at least one ofsadi connectors including an integral bifurcated portion the branches ofwhich are separated from one another and means for adjusting the spacingbetween said branches, the junction of said bifurcated portion and oneof the branches of said portion being fixed in relation to differentones of the support and an end of said element, whereby adjustment ofsaid spacing between said branches results in displacement of said endand the support in substantially one direction.
 2. On-board vehicleweight transducer apparatus as set forth in claim 1 wherein saidbifurcated portion is formed by a slot and an enlarged hole at theclosed end of the slot, material between the hole and nearby externalsurfaces of said connector being of reduced cross-section and therebyforming two relatively deformable flexures one on each side of the slot.3. On-board vehicle weight transducer apparatus as set forth in claim 1wherein siad junction is fixed in relation to an end of said element,and wherein said securing means mounts one of said branches in fixedrelation to the support at one of the longitudinally-spaced positionstherealong.
 4. On-board vehicle weight transducer apparatus as set forthin claim 3 wherein said junction is integrally united with said end ofsaid element, wherein said means for adjusting the spacing between saidbranches comprises a nut and bolt for adjustably drawing said branchescloser together, and wherein said bolt further mounts said one of saidbranches in said fixed relation to the support.
 5. On-board vehicleweight transducer apparatus as set forth in claim 1 wherein said one ofsaid branches is fixed in relation to an end of said element, andwherein said securing means mounts said junction in fixed relation tothe support at one of said positions.
 6. On-board vehicle weighttransducer apparatus as set forth in claim 5 wherein said one of saidbranches in integrally united with said end of said element, and whereinsaid means for adjusting said spacing between said branches comprises aset screw threadedly engaged with one of said branches and having an endabutting the other of said branches, whereby adjustment of said setscrew adjustably spreads said branches apart.
 7. On-board vehicle weighttransducer apparatus as set forth in claim 1 for use with such a supportwhich includes a pair of lugs externally thereof and integrallytherewith, one at each of the spaced positions and in substantiallyhorizontal alignment, and wherein said securing means secures saidconnectors to the external lugs of the support, the one of said junctionand branches which is fixed in relation to the said end of said elementbeing integrally united therewith.
 8. On-board vehicle weight transducerapparatus as set forth in claim 7 for use with such a support in whichthe lugs are substantially aligned with a horizontal plane including theneutral axis of the support, and wherein both of said connectors includean integral bifurcated portion and are substantially the same.